/*
 * Copyright 2014 Red Hat, Inc.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * and Apache License v2.0 which accompanies this distribution.
 *
 * The Eclipse Public License is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * The Apache License v2.0 is available at
 * http://www.opensource.org/licenses/apache2.0.php
 *
 * You may elect to redistribute this code under either of these licenses.
 */

package io.vertx.ext.auth.mongo.impl;

import io.vertx.core.AsyncResult;
import io.vertx.core.Future;
import io.vertx.core.Handler;
import io.vertx.core.impl.logging.Logger;
import io.vertx.core.impl.logging.LoggerFactory;
import io.vertx.core.json.JsonObject;
import io.vertx.ext.auth.HashingStrategy;
import io.vertx.ext.auth.User;
import io.vertx.ext.auth.authentication.CredentialValidationException;
import io.vertx.ext.auth.authentication.Credentials;
import io.vertx.ext.auth.authentication.UsernamePasswordCredentials;
import io.vertx.ext.auth.impl.UserImpl;
import io.vertx.ext.auth.mongo.*;
import io.vertx.ext.mongo.MongoClient;

import java.util.List;
import java.util.Map;

/**
 * An implementation of {@link MongoAuthentication}
 *
 * @author mremme
 */
public class MongoAuthenticationImpl implements MongoAuthentication {

  private static final Logger log = LoggerFactory.getLogger(MongoAuthenticationImpl.class);

  private final HashingStrategy strategy = HashingStrategy.load();
  private MongoClient mongoClient;
  private MongoAuthenticationOptions options;
  private HashStrategy legacyStrategy;
  private String hashField;

  /**
   * Creates a new instance
   *
   * @param mongoClient
   *          the {@link MongoClient} to be used
   * @param options
   *          the options for configuring the new instance
   */
  public MongoAuthenticationImpl(MongoClient mongoClient, MongoAuthenticationOptions options) {
    this.mongoClient = mongoClient;
    this.options = options;
  }

  /**
   * Provided for backward compatibility
   * @param mongoClient
   * @param legacyStrategy
   * @param options
   */
  public MongoAuthenticationImpl(MongoClient mongoClient, HashStrategy legacyStrategy, String hashField, MongoAuthenticationOptions options) {
    this.mongoClient = mongoClient;
    this.options = options;
    this.legacyStrategy = legacyStrategy;
    this.hashField = hashField;
  }

  @Override
  public void authenticate(JsonObject credentials, Handler<AsyncResult<User>> resultHandler) {
    authenticate(new UsernamePasswordCredentials(credentials), resultHandler);
  }

  @Override
  public void authenticate(Credentials credentials, Handler<AsyncResult<User>> resultHandler) {
    try {
      // Null username is invalid
      if (credentials == null) {
        resultHandler.handle((Future.failedFuture("Credentials must be set for authentication.")));
        return;
      }

      UsernamePasswordCredentials authInfo = (UsernamePasswordCredentials) credentials;
      authInfo.checkValid(null);

      AuthToken token = new AuthToken(authInfo.getUsername(), authInfo.getPassword());

      JsonObject query = createQuery(authInfo.getUsername());
      mongoClient.find(options.getCollectionName(), query, res -> {

        try {
          if (res.succeeded()) {
            User user = handleSelection(res, token);
            resultHandler.handle(Future.succeededFuture(user));
          } else {
            resultHandler.handle(Future.failedFuture(res.cause()));
          }
        } catch (Exception e) {
          log.warn(e);
          resultHandler.handle(Future.failedFuture(e));
        }

      });
    } catch (ClassCastException | CredentialValidationException e) {
      resultHandler.handle(Future.failedFuture(e));
    }
  }

  /**
   * The default implementation uses the usernameField as search field
   *
   * @param username
   * @return
   */
  protected JsonObject createQuery(String username) {
    return new JsonObject().put(options.getUsernameField(), username);
  }

  /**
   * Examine the selection of found users and return one, if password is fitting,
   *
   * @param resultList
   * @param authToken
   * @return
   */
  private User handleSelection(AsyncResult<List<JsonObject>> resultList, AuthToken authToken)
      throws Exception {
    switch (resultList.result().size()) {
    case 0: {
      String message = "No account found for user [" + authToken.username + "]";
      // log.warn(message);
      throw new Exception(message);
    }
    case 1: {
      JsonObject json = resultList.result().get(0);
      User user = createUser(json);
      if (examinePassword(user, json.getString(options.getPasswordCredentialField()), authToken.password))
        return user;
      else {
        String message = "Invalid username/password [" + authToken.username + "]";
        // log.warn(message);
        throw new Exception(message);
      }
    }
    default: {
      // More than one row returned!
      String message = "More than one user row found for user [" + authToken.username + "( "
          + resultList.result().size() + " )]. Usernames must be unique.";
      // log.warn(message);
      throw new Exception(message);
    }
    }
  }

  private User createUser(JsonObject json) {
    User user = new UserImpl(json);
    if (legacyStrategy != null) {
      json.put(MongoAuthImpl.PROPERTY_FIELD_SALT, hashField);
      json.put(MongoAuthImpl.PROPERTY_FIELD_PASSWORD, options.getPasswordField());
    }
    return user;
  }

  private boolean examinePassword(User user, String hash, String password) {

    if (hash.charAt(0) != '$') {
      // this isn't a phc-string, it's legacy
      if (legacyStrategy == null) {
        throw new IllegalStateException("Mongo Authentication cannot handle legacy hashes without a HashStrategy");
      }

      String givenPassword = this.legacyStrategy.computeHash(password, user);
      return hash.equals(givenPassword);
    } else {
      return strategy.verify(hash, password);
    }
  }

  @Override
  public String hash(String id, Map<String, String> params, String salt, String password) {
    return strategy.hash(id, params, salt, password);
  }


  /**
   * The incoming data from an authentication request
   *
   * @author mremme
   */
  static class AuthToken {
    String username;
    String password;

    AuthToken(String username, String password) {
      this.username = username;
      this.password = password;
    }
  }
}
